A retrospective study of dystocia-related vertebral fractures in neonatal calves.

Forty-seven cases of neonatal vertebral fractures/luxations occurred in a 21 year period (1967-1987). All of the fractures were located between the 11th thoracic vertebra and the fourth lumbar vertebra; 77% occurred at the thoracolumbar junction. All but one case was associated with a forced extraction, either unspecified (53%), mechanical (28%), or manual (17%).A weak calf or continuous recumbency since birth was the major clinical sign. Hemorrhage around the kidneys, adrenal glands, and in perivertebral muscles was a consistent necropsy finding and a useful indicator that a thoracolumbar fracture was present. In addition to the vertebral fracture, the prominent necropsy findings were subdural and epidural hemorrhage, myelomalacia, spinal cord compression or severed spinal cord, and fractured ribs. All of the calves died or were euthanized without regaining locomotory function.

Temperature and neuromuscular development in embryos of the trout (Salmo trutta L.).

Myogenesis and neural development were examined in the myotomes of trout (Salmo trutta L.) embryos reared at 2, 6 and 10 degrees C. The relative timings of myotube and muscle fibre formation were similar, with respect to somite stage, at all three temperatures. Myogenesis was seen to begin medially, adjacent to the notochord, and also in separate zones located near the outer surface of the myotomes, believed to be the sites of formation of future slow muscle fibres. Temperature did not affect the relative timings of most aspects of neural development, including HNK-1-immunoreactivity of myosepta, primary motor neuron axonogenesis, Rohon-Beard dendrite outgrowth, and expression of acetylcholinesterase in the spinal chord and at the myosepta. The posterior progression of the lateral line primordium was slightly but significantly delayed relative to somite stage in embryos reared at 10 degrees C compared to 6 and 2 degrees C, while formation of vacuoles in the notochord occurred relatively earlier at higher temperatures. No significant differences in neuromuscular development were observed between offspring of migratory and of non-migratory females.